Renal Physiology II

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Renal Physiology II

• Nermien Waly MD, PhD
• Lecturer
• School of Pharmacy
• R1339
• ACU
• nwaly_at_yahoo.com

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Kidney functions

• Excretory function
• a. urine formation,
• b. micturition,
• c. urinalysis.
• 2. Regulatory functions e.g.
• a. Water balance,
• b. Electrolyte balance,
• c. Acid-base balance (pH).
• d. Osmolarity regulation.
• e. Regulation of ABP
• 3.Endocrine function renin, erythropoietin.

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1.Water balance
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Body water

• 60 of body weight is water
• 40 of body weight is ICF (intracellular)
• 20 of body weight is ECF (extracellular)
• TBW concept

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ICF ECF

• Intracellular
• 
  
• 2/3rd of body water
• K, Mg, protein
• pH acidic
• Osmolarity 290

• Plasma, interstitial fluid
• 1/3rd of body water
• Na,Cl-, HCO3-
• pH alkaline
• Osmolarity 290

• Osmolarity is concentration of particles in
  solution expressed as osmole per liter
• pH is the logarithmic expression of hydrogen ion
  concentration

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• Regulation of TBW, Osmolarity, and electrolyte
  balance via Kidneys occurs through the following
  mechanisms
• Control the volume of urine
• Control the secretion of electrolytes
• Urine concentration or dilution

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2.Endocrine function of kidney

• Erythropoietin (EPO) secretion
• Glycoprotein, m.wt.34,000
• Stimulate BM to produce RBCs, initiate Hb
  synthesis
• Excess EPO produce Polycythemia, heart attacks
• Banned as an enhancing drug by Tour De France
  org. and others

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• Renin secretion
• Enzyme secreted by juxta-glomerular cells of
  afferent arterioles
• In plasma
• Angiotensinogen Renin Angiotensin I
• In lungs
• Angiotensin I ACE Angiotensin II
• Angiotensin II effects Aldosterone secretion,
  vasoconstriction
• ACE inhibitors (Captopril), AT1 inhibitors
  (Losartan)

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3.Acid-base balance

• Acid H donor HA
• Base H acceptor A-
• p function - Log of X e.g. H
• pH acidity or basicity of a sol. neutral at 7
• pK strength of an acid
• Buffer is a sub. That prevent the change of the
  pH of the sol. When H are added or removed

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a. Buffers

• Definition
• Buffer pair weak acid and its salt e.g. H2CO3- /
  Na HCO3-
• Effectiveness of buffer pair
• pH pK log A-/HA
• Buffers in biology

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IC EC
b. Biologically significant buffers

• Protein Hemoglobin
• Deoxy Hb vs. oxy Hb, major IC buffer
• Organic phosphates
• 2,3 DPG
• 
  

• CO2/HCO3- major EC buffer
• Phosphates H2PO4/HPO4-2
• Urinary buffer, titratable acid

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c. Renal acid-base balance

• Re-absorption of HCO3-

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c. Renal acid-base balance (cont.)

• 2. Execretion of fixed H
• As titratable acids (H2PO4)

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c. Renal acid-base balance (cont.)

• 2. Execretion of fixed H
• As NH4

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d. Acid-base disorders

• Acidosis/ acidemia
• overproduction of acids or loss of base.
• Either metabolic (ketoacidosis, diarrhea) or
  respiratory (opiates)
• Alkalosis/alkalemia
• overproduction of base or loss of acid.
• Either metabolic (vomiting) or respiratory
  pneumonia, salicylates)

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Kidney functions

• Excretory function
• a. urine formation,
• b. micturition,
• c. urinalysis.
• 2. Regulatory functions e.g.
• a. Water balance,
• b. Electrolyte balance,
• c. Acid-base balance (pH).
• d. Osmolarity regulation.
• e. Regulation of ABP
• 3.Endocrine function renin, erythropoietin.

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Happy Easter